The present invention relates to generally a wall construction capable of withstanding the forces caused by heat and pressure and a method for constructing the same and more particularly a reinforced concrete shield wall for surrounding reactor containment vessel for a nuclear power station and a method for constructing the same and has for its object to increase the resistance of the concrete shield wall against heat and/or pressure and to provide an improved method for constructing the same.
It has been well known in the art to line the exterior surface of a pressure vessel with a heat insulator such as glass fiber, rock wool or the like in order to minimize the heat dissipation from a reactor core or a nuclear thermal source, thereby improving the thermal efficiency.
The present invention relates to a reinforced concrete shield wall surrounding a reactor containment vessel, the interior surface of the concrete shield wall being lined with a heat insulator in order to attain the effects different from those attained by lining the exterior surface of the pressure vessel.
A reactor building biological shield wall (concrete shield wall) is in general spaced apart from a reactor containment vessel by approximately 50 mm and is designed so as to withstand the sudden temperature and pressure rise resulting from the loss of part or the whole of the coolant due to a rupture in the coolant system in the reactor system. In case of a failure of the coolant system the heat is more critical than the pressure with the civil design. In order to withstand the thermal stresses the concrete shield wall is reinforced with steel rods or bars. For instance, in case of a concrete shield wall thickness of approximately 1900 mm, longitudinal reinforcements such as longitudinal steel bars or the like are arrayed in three coaxial circles spaced radially from each other by 200 mm and the longitudinal reinforcements in each circle are circumferentially spaced apart from each other by 200 mm.
Adjacent to or interconnected to each of the circles of the longitudinal reinforcements, horizontal reinforcements such as horizontal steel bars or the like which are vertically spaced apart from each other by about 200 mm are also arranged. Of three circles of longitudinal reinforcements, two circles together with the horizontal reinforcements are arranged in order to withstand the thermal stresses while the remaining circle having the horizontal reinforcements is arranged in order to absorb the shocks in case of an earthquake and the weight of the concrete shield wall. Both the longitudinal steel reinforcements and the horizontal steel reinforcements are approximately 38 mm in diameter (D38). The three circles of longitudinal reinforcements are located adjacent to both sides of the interior and exterior wall surfaces. That is, the total of six circles of longitudinal reinforcements and the horizontal reinforcements associated therewith are embedded in the concrete shield wall.
The longitudinal reinforcements serve as resistance members to protect the shield wall from tension loads when acting in the longitudinal direction, and the horizontal reinforcements resist tension loads in the circumferential direction.
These longitudinal and horizontal reinforcements make a complex space structure which restricts the flow of concrete upon placing, especially the aggregate in the concrete flow.
Thus, complicated reinforcements cause problem when pipes and holes are made to pass through the shield wall.